Glaucoma drops may cause vision loss


Glaucoma drops may cause vision loss

Beta-blocker eyedrops, commonly used to treat glaucoma, may put some people with the condition at increased risk for further visual loss by aggravating the fall of blood pressure during sleep, according to a University of Iowa (UI) Health Care study.

This excessive nighttime fall in blood pressure in susceptible individuals can interfere with optic nerve circulation which, in turn, may worsen glaucoma damage and produce an optic nerve stroke, known as anterior ischemic optic neuropathy, said Sohan Singh Hayreh, M.D., Ph.D., D.Sc., UI College of Medicine professor emeritus of ophthalmology and visual sciences, and lead author.

"Blood pressure normally falls during sleep in all of us, and it is not a problem if there are no other risk factors," Dr. Hayreh said. "However, if a person with glaucoma is taking beta-blocker eyedrops to lower eye pressure, the blood pressure could fall even more and potentially reduce blood circulation through the optic nerve in susceptible individuals."

Although these beta-blocker eyedrop side effects had been previously documented, the UI planned study is the first to examine the problem on a large-scale by continuous blood pressure monitoring over a 24-hour period. The UI team studied 275 white patients, 161 with glaucoma and 114 who had experienced an eye stroke.

Participants had their blood pressure monitored every 10 minutes during the daytime and every 20 minutes during the nighttime for 24 hours.

"We were surprised to find that patients with normal tension glaucoma, also known as low tension glaucoma, had much greater decreases in blood pressure than patients who were known to have the optic nerve stroke," Hayreh said.

Patients using beta-blocker eyedrops had much greater decreases in nighttime diastolic blood pressure, lower minimum nighttime diastolic blood pressure, and lower minimum nighttime heart rate than patients who were not using the medication.

Thus, beta-blocker eyedrop use may put individuals at risk for optic nerve stroke or worsened glaucoma damage.

Previous studies led by Hayreh have shown a significant association between progressive vision deterioration and nighttime blood pressure fall in patients with glaucoma or optic nerve stroke who also had high blood pressure and were on blood pressure lowering medication.

Beta-blockers are one of many types of pills used to lower high blood pressure. The UI studies seem to suggest that beta-blockers taken orally as a pill or in eyedrop form can cause excessive blood pressure fall during sleep, particularly when the medication is taken at bedtime or in the evening.

The excessive blood pressure decrease is then a risk factor for glaucoma damage or optic nerve stroke. These risks also hold true for other blood pressure-lowering medicines.

"It is absolutely essential for people with glaucoma to lower their eye pressure," he said. "However, the present research study suggests that for some individuals beta-blocker eyedrops may not be the ideal medication to use.

"If a person with glaucoma is using beta-blocker eyedrops and yet is still losing vision in spite of low eye pressure, the nighttime blood pressure decrease may be the underlying fact In that case, it is better to switch to other glaucoma drops that do not decrease the blood pressure too much during sleep."

Hayreh cautioned that people using beta-blockers, whether in eyedrop from for glaucoma or pill form for high blood pressure, should not stop taking their medication on their own because that can be extremely dangerous. Instead they should consult with their ophthalmologist or other physician about whether they are at increased for problems and should thus adjust their treatment.

Approximately two million Americans have glaucoma. Overall, it is the second most common cause of legal blindness. Glaucoma painlessly destroys side vision, thus limiting a person's ability to perform most day-to-day activities such as walking, driving or carrying out manual tasks. A person with glaucoma can deceptively believe that his or her eyes are fine because central vision is generally lost only in the late stages of the disease. Left untreated, glaucoma damage is irreversible and progressive, ultimately resulting in complete blindness.

SOURCES: American Journal of Ophthalmology, September 1999.

"Common Glaucoma Treatment May Increase Other Eye Risks," media advisory, University of Iowa College of Medicine, Nov. 3, 1999.

The Chiropractic Journal.

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